Postmortem explants of human trabecular meshwork from 23 eyebank eyes had a growth rate of 32% (71/160) cultures, with 8% (12) showing abundant cellular spread. One hundred percent confluency was achieved with eyes from donors of 11 to 40 years of age. One of the cultures grew profusely and we were able to study it through eight passages in culture. This culture had the morphologic characteristics described by Polansky et al. for cultured human trabecular meshwork cells. A sensitive radioimmunoassay for fibronectin in tissue culture supernatant showed an increase in fibronectin secretion over a 96 hr period, with a characteristic shift-down response occurring between 24 and 48 hr postmedia change. Three of four cultures showed the presence of laminin, a basement membrane protein, establishing that the cells are not fibroblasts.